• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1545-1561
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• 2008

Among all transportations, railway transports have been promisingly offering excellent energy conservation and travelling time. Inevitably, they become a main role in not only transport goods but also passengers. With leap in development of technology, trains have tremendously enhanced their services in terms of speed, accessibility and comfort. However, the safety and ride quality have become a main issue as the train speed increased. The higher speeds have led the structural dynamics and health must be monitored from time to time to ensure that they are in good condition to provide reliable ride. Among all monitoring systems, the structural health monitoring (SHM) systems are imperative important due to its capability of in-situ monitoring and inherently reduce the maintenance frequencies and the huge associated cost. In this paper, SHM systems and the related non-destructive test and evaluation methods were discussed. The types of damages related to train vehicles as well as the damage hot spots are also included in this paper.

• 항공우주시스템공학회지
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• 제9권3호
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• pp.8-11
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• 2015

Since the late 1990's, FAA, NASA and the aerospace industry have worked together to develop the sharing system of the composite material qualification databases which were obtained through the standardized fabrication and testing procedures. The result was what is now known as the AGATE(Advanced General Aviation Transport Experiments) or NCAMP(National Center for Advanced Materials Performance) methodology, a more cost-effective concept that shifts the major responsibility for qualification and testing from the aircraft manufacturer to the material supplier. The properties of composite materials are largely dependent on the testing as well as the raw material properties and the manufacturing process including the process control parameters. Thus it is important in the composite material qualification to comply with the standardized testing procedures. In this paper, I will describe the standardized witness methodologies of certification engineers to reduce the effect of testing variability within the qualification data.

• 전기학회논문지
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• 제68권1호
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• pp.129-139
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• 2019

In order for a gun-launched guided projectile to glide to the maximum range, when to deploy the fin and start flight with guidance and control should be considered in range optimization process. This study suggests a solution to the optimal guidance problem for flight range maximization of the flight model of a guided projectile in vertical plane considering the aerodynamic properties. After converting the nonlinear Multi-Phase Optimal Control Problem to Two-Point Boundary Value Problem, the optimized guidance command and the best fin deployment timing are calculated by the proposed numerical method. The optimization results of the multiple flight rounds with various initial velocity and launch angle indicate that determining specific launch condition incorporated with the guidance scheme is of importance in terms of mechanical energy consumption.

• International Journal of Internet, Broadcasting and Communication
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• 제14권3호
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• pp.258-269
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• 2022

In these days, innovative functions are required to unmanned parcel delivery lockers. As non-face-to-face transactions become the center due to the recent COVID-19 pandemic, many problem occurs in society such as theft crimes and lack of loading space. Therefore, New concept storage device is developed in korea. It has the functions that minimizes empty spaces by using the internal transport device to enable efficient space loading and refrigerate goods such as foods. In order to systematically approach the system design of the unmanned parcel delivery lockers which is the new function is applied, We applied model-based system engineering to improve the development efficiency and use a system modeling language to express the system. We conducted interworking research of CAD data including system modeling and design data. it is expected that this method will increase the effective development efficiency such as maintenance traceability and reduction of development period and cost.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2023년도 춘계학술대회
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• pp.252-253
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• 2023

Container terminal automation might offer many potential benefits, such as increased productivity, reduced cost, and improved safety. Autonomous trucks can lead to more efficient container transport. A robust lane detection method is proposed using score-based generative modeling through stochastic differential equations for image-to-image translation. Image processing techniques are combined with Density-Based Spatial Clustering of Applications with Noise (DBSCAN) and Genetic Algorithm (GA) to ensure lane positioning robustness. The proposed method is validated by a dataset collected from the port terminals under different environmental conditions and tested the robustness of the lane detection method with stochastic noise.

• 한국항공운항학회지
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• 제31권4호
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• pp.28-44
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• 2023

This study investigates aircraft lessor business models by studying cases and interviewing experts to analyze investors and business strategies of aircraft lessor. The results confirm that there is a wide range of investors including institutional investors, financial institutions, insurance companies, corporations, and wealthy individuals for aircraft lessor. Aircraft lessors can be categorized based on its required rate of return (cost of capital) into bank-investing core, institutional investor-investing value-added, and hedge fund-investing opportunistic. Aircraft lessor decides leasing rate by aircraft purchasing price and lessee's credit rating. Core aircraft lessors invest in new aircrafts for new placement or sale-and-leaseback strategy requiring little technical risk in aircraft, value-added lessors invest in middle-aged aircrafts for re-leasing, opportunistic lessors invest in old aircrafts for freighter conversion or part-out strategy requiring high level of expertise. This study provides insights for future Korean aircraft lessor establishment and investment.

• 대한의용생체공학회:의공학회지
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• 제45권2호
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• pp.57-65
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• 2024

Recently, several studies have been conducted to lower the cost of transport of human by adding external joint stiffness elements. However, it has not been clearly elucidated whether adaptation time is required for human subjects to adapt to the added external joint stiffness. In this study, carbon plates in the form of shoe midsoles were added to the metatarsophalangeal joint, and the lower limb joint torque and mechanical energy consumption were compared before and after a total of 5 sessions (2.5 weeks) of running. A total of 11 young healthy participants exhibited higher elastic energy storage in carbon plates in the fifth session compared to the first session, and lower power in the ankle joint. This suggests that a single training session may be insufficient to validate the efficiency effect of added joint stiffness, and the human body seems to increase the elastic energy stored in the assistive joint stiffness and its reutilization.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.277-278
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• 2023

In 2022, construction had a five fold higher accident and fatality rate compared to the overall industry. The Construction Technology Promotion Act requires parties in construction contracts to calculate safety costs following Ministry of Land, Infrastructure and Transport guidelines. Understanding safety expense components is vital for evaluating accident prevention costs and planning anti-accident strategies. A study surveyed safety professionals to analyze the importance and influence of safety management expense components, providing basic data for future research. Survey results highlighted the significance of safety management plans, structural safety assurance, and preventing collateral damage.

• Safety and Health at Work
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• 제10권4호
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• pp.452-460
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• 2019

Background: Monitoring and control of PM_2.5 are being recognized as key to address health issues attributed to PM_2.5. Availability of low-cost PM_2.5 sensors made it possible to introduce a number of portable PM_2.5 monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scatteringe-based PM_2.5 monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM_2.5 sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy. Methods: This study discussed the calibration of a low-cost PM_2.5-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM_2.5 sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM_2.5. Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference. Results: Based on the performance of ML algorithms used, regression of the output of the PMD to PM_2.5 concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 ㎍/㎥, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol. Conclusions: Calibration of a low-cost PMD, which is based on construction of PM_2.5 sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

• 대한교통학회지
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• 제17권1호
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• pp.41-52
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• 1999

'90년대 들어 미국을 중심으로 Double Counting 문제와 Keynesian/Neo-classical economics theory 까지 연계되어 교통투자가 경제성장에 거의 영향을 주지 않는다는 이론과 영향을 많이 준다는 상충되는 연구결과가 계속 발표되었다. 본 논문은 교통에 대한 투자가 경제성장에 미치는 영향을 계량적으로 분석한 것이다. 범위를 좁혀 도로에 대한 투자가 생산성 즉 제조업체의 물류비에 미치는 영향을 Stated Preference Technique를 이용하여 분석한 것이다. 도로이용 승객의 시간가치를 추정하는 일반적인 Cost/Benefit Analysis와는 달리 화물수송과 관련된 투자효과를 분석하였다. 먼저 도로에 대한 투자가 화물의 수송시간절약과 그에 따른 창고시설, 재고관리등에 미치는 영향을 continuous review system과 periodic review system으로 나누어 이론적으로 고찰하였다. 또한 본 논문에서는 Utility Model에 기초하여 시간가치(value of time)와 화물도착의 정확성 (value of reliability)을 도착지별(depot/consumer)과 상품별로 econometrics 기법을 활용 분석한 후 영국의 COBA와 비교 검토하였다. 종합적으로 도로에 대한 투자가 시간절약, 운행비용절감, 사고비용절감 등 직접적인 효과(direct benefit)외에 depot감소, 운행차량감소, 재고비용절약, 유휴자원의 활용 등(secondary benefits)을 통하여 경제성장에 긍정적인 영향을 끼치고 있는 것으로 나타났다.